Pressure to Sell Cheongung-II to Ukraine: The United States’ Multiple Demands and South Korea’s Policy Options

Executive Summary

President Trump's public pressure on South Korea to sell the Cheongung-II missile defense system to Ukraine stems from the structural limitations of the U.S. defense industrial base, which is struggling to meet simultaneous demands from three fronts: Iran, Ukraine, and the Indo-Pacific. This pressure is linked to demands for a troop deployment to the Strait of Hormuz, defense cost-sharing contributions, and semiconductor tariff negotiations, forming a single package. Addressing these issues on separate tracks could result in South Korea forfeiting its negotiating leverage. The most likely scenario is that the South Korean government will delay a decision, neither clearly approving nor rejecting the sale. A procurement method via the United States, modeled on the precedent of indirectly selling 155mm artillery shells, is being discussed as a realistic compromise. However, given the precedent of U.S. ammunition sales policy shifting between suspension and resumption, the stability of such an agreement is not guaranteed. South Korea needs to unify its messaging across government ministries and adopt a modest approach, responding conditionally and incrementally within the bounds of what its relationship with Russia and domestic public opinion can tolerate.

I. Situational Analysis

Trump-Driven Pressure to Sell Cheongung-II to Ukraine: A Situational Analysis

1. Background and Developments

President Trump's pressure on South Korea is not an isolated remark but a continuation of a trend that has been building since last summer. The issue first arose in the context of the war with Iran. On August 16, President Trump announced on Truth Social that he had instructed Secretary of Defense Hegseth to significantly scale back U.S.-South Korea joint military exercises. In the same post, he mentioned, "I recently asked the South Korean president if he was willing to join the effort to denuclearize Iran, but was told he would 'decline'"[1][17].

Following this statement, the South Korean government began reviewing a troop deployment to the Strait of Hormuz. Options such as dispatching a logistics support ship or patrol aircraft were discussed in a joint meeting of foreign and security ministries[8]. A senior official from the President's Office confirmed that "military contribution" options related to the Strait of Hormuz were under review but drew a line, stating that nothing had been decided[16]. In a Fox News interview released on August 30, President Trump again singled out South Korea as "a prime example" of allies on whom the U.S. spends billions of dollars, including NATO, yet receives "almost no help" in return[5]. He also brought up the issue of South Korea's refusal to support mine-clearing operations in the Strait of Hormuz[5].

The scope of the pressure did not stop there, expanding to the issue of Ukraine. On September 4 (KST), President Trump shared a column on his social media platform arguing that "South Korea should sell its domestically produced Cheongung-II anti-aircraft missiles to Ukraine"[1][4]. On the same day, in response to a media inquiry about South Korea's review of a Hormuz deployment, a senior U.S. administration official replied, "South Korea is one of the largest customers of Middle Eastern crude oil," adding, "We are still waiting for South Korea to deploy resources to this region"[4]. In effect, the demand for a troop deployment and the demand for an arms sale were made simultaneously on the same day.

2. Current Situation

On the Ukraine issue, the U.S. pressure campaign is not aimed solely at South Korea but is simultaneously expanding to Europe. In a separate social media post on September 3, President Trump announced he would demand that European countries repay the tens of billions of dollars in military aid provided free of charge to Ukraine and NATO during the Biden administration[10][14]. This statement came shortly after reports that U.S. ammunition stockpiles were being depleted as the war with Iran entered its seventh month[10]. While President Trump strongly denied the rumors of ammunition depletion, he also suggested that ammunition sales to allies could be temporarily suspended[6][12]. However, a few days later, he mentioned that sales to allies would resume soon, showing a lack of consistency in his messaging[11].

To fill this gap, Ukraine has turned to the European Union. Ukraine requested funds to purchase Patriot PAC-3 interceptor missiles using a €90 billion aid loan approved by the EU, and on September 2, EU Commission President von der Leyen confirmed that Europe would continue its air defense support and assistance with the Patriot system[19]. In this context, South Korea's Cheongung-II is being discussed as a potential substitute to fill the gap in U.S. ammunition and weapons supply.

Regarding the Hormuz deployment, a cautious stance is evident within South Korea. In an editorial, the Hankyoreh newspaper stated, "When it comes to a deployment that puts citizens' lives at risk, one can never be too cautious," and warned against the government rushing a deployment under U.S. pressure[1]. The same newspaper highlighted the government's dilemma by reporting on the division in domestic public opinion between "indirect deployment" and "no participation in a war of aggression"[4].

3. Key Actors and Positions

President Trump and the U.S. AdministrationThis actor has repeatedly demanded that South Korea share responsibility by linking security and economic issues. An EAI analysis assesses this pressure not as "impromptu rhetoric but as structural pressure based on the 'ending free-riding' logic presented by Steve Myron, Chairman of the White House Council of Economic Advisers"[5]. It is assessed that targeted semiconductor tariffs, designation as a transshipment risk country, and defense cost-sharing demands are likely to be linked as a single negotiating package[5]. The senior U.S. administration official's use of the logic that "South Korea is the largest customer of Middle Eastern crude oil" in relation to the Hormuz deployment is an extension of this linked pressure[4].

The South Korean Governmentis maintaining a cautious stance on both the deployment and arms sale demands. The President's Office has repeatedly stated that it is "reviewing various options" regarding Hormuz but that "nothing has been decided"[16]. The government has not announced an official position on the sale of Cheongung-II to Ukraine, as the issue is entangled with relations with Russia and policy toward China.

South Korean Public Opinion and Mediaexpress clear apprehension about the troop deployment. In two editorials, the Hankyoreh assessed the U.S. pressure as being "beyond the level of international custom and common sense," yet maintained the principled stance that even if the pressure is burdensome, caution is necessary for a "deployment that puts citizens' lives at risk"[17][1].

Some U.S. Observers and Officialspoint to the risks of the social media pressure tactic itself. The Council on Foreign Relations (CFR) mentioned the precedent of South Korea having already sold 100,000 rounds of 155mm artillery shells to the U.S. in 2022 for delivery to Ukraine. Citing this and South Korea's expansion of arms development and technology cooperation with European countries, the CFR assessed that public pressure via social media could actually become a risk factor in alliance management[2].

UkraineAmid signals of reduced U.S. support, is broadening its support base to Europe while also showing interest in the possibility of acquiring alternative weapon systems like South Korea's Cheongung-II. The resignation of U.S. Secretary of the Army Dan Driscoll, who was a strong advocate for Ukraine aid, is also cited as circumstantial evidence suggesting a shift in the U.S. stance on supporting Ukraine[18].

Other Asian Allies, Including Taiwanare also exposed to a similar pressure structure. Taiwan is experiencing delays in the delivery of $14 billion worth of Patriot PAC-3 and NASAMS air defense systems. The acting U.S. Under Secretary of the Navy cited a "temporary suspension" to secure ammunition needed for operations in Iran (Epic Fury) as the reason[9]. This shows that the pressure South Korea faces regarding weapons and ammunition is not an isolated issue but a structural phenomenon linked to the overall shortage of U.S. ammunition stockpiles[9][21].

4. Key Issues

The first issue is the nature of the demand. It is unclear whether the pressure to sell the Cheongung-II is simply a recommendation to export arms or a negotiating card tied to a package deal that includes the Hormuz deployment and defense cost-sharing. An EAI analysis presents the most likely scenario as one in which pressure is applied concurrently on both tariff and security tracks[5].

The second issue is relations with Russia. If South Korea directly sells lethal weapons to Ukraine, the question remains of how the government will manage the repercussions for its diplomatic relations with Russia and the North Korea-Russia military cooperation framework.

The third issue is the government's response system. EAI has previously pointed out the need for a unified control tower, noting that "if the responses of the Ministry of Trade, Industry and Energy, the Ministry of Foreign Affairs, and the Ministry of National Defense are fragmented, there is a risk that the U.S. side will exploit differences in their positions to maximize concessions"[5]. This point is particularly relevant in the current situation, where demands for a troop deployment and an arms sale are being made simultaneously.

II. In-Depth Analysis

Trump-Driven Pressure to Sell Cheongung-II to Ukraine: An In-Depth Analysis

1. Analysis of Root Causes

The surface-level cause of this pressure is the U.S. military's ammunition stockpile. Reports have emerged that U.S. ammunition consumption has accumulated as the war with Iran enters its seventh month[10]. President Trump strongly denied these reports. However, while denying them, he simultaneously suggested the possibility of a temporary halt in ammunition sales to allies[6][12]. The strength of his denial contradicts the direction of his proposed action. This can be read as circumstantial evidence that the stockpile problem is real.

A deeper cause is the structural limitation of the U.S. defense industrial base. The delay in delivering $14.5 billion worth of Patriot PAC-3 and NASAMS systems to Taiwan is a prime example. In Senate testimony, the acting Under Secretary of the Navy stated that arms sales to Taiwan were being "temporarily suspended" to secure ammunition needed for operations in Iran (Epic Fury)[9]. Some observers have also pointed out that Asian allies are bearing the costs of the Iran stalemate[21]. In other words, the U.S. production capacity is unable to meet the simultaneous demands of three fronts: Iran, Ukraine, and the Indo-Pacific.

At this juncture, the reason South Korea has been targeted is clear. South Korea has a precedent of indirectly supporting Ukraine by selling 100,000 rounds of 155mm artillery shells to the United States[2]. This means it already has a proven indirect supply route. At the same time, it is one of the few countries that possesses its own air defense system, the Cheongung-II, which has capabilities similar to the Patriot system. From the U.S. perspective, this means it is an alternative that can meet Ukraine's air defense needs without going through U.S. production lines. President Trump's act of personally sharing a column advocating for the sale to Ukraine[1][4] should be seen not as an impulsive tweet but as a signal designating South Korea as a candidate to fill this structural gap.

2. Structural Context

Security Structure: The Simultaneous Arrival of Multiple Bills

The bill presented to South Korea is not a single one. First came dissatisfaction with its refusal to cooperate on Iran's denuclearization[17], which led to a review of a troop deployment to the Strait of Hormuz[8][16]. On the same day, a senior U.S. administration official pressed for the deployment of resources, stating that "South Korea is one of the largest customers of Middle Eastern crude oil," while President Trump shared the column on the Cheongung-II sale[4]. The overlap of the deployment demand and the arms sale demand at the same time should be seen not as a coincidence but as a strategy of diversified pressure. It is a method of opening another track if concessions are not obtained on one.

This structure is also connected to pressure for defense cost-sharing, increased defense spending, and the procurement of U.S.-made weapons. There is the precedent of the first Trump administration demanding Germany spend 2% of its GDP on defense and playing the card of withdrawing U.S. forces from Germany[3]. In his second administration, NATO members have agreed to increase defense spending to 5% of GDP by 2035[3]. The same logic is being applied to South Korea and Japan[3]. The 'ending free-riding' logic presented by Steve Myron, Chairman of the White House Council of Economic Advisers, is the theoretical foundation for all this pressure[5][7]. It signifies that the United States will no longer bear the cost of providing the public goods of security and economy alone[7].

Political Structure: A Transactional View of Alliances and Unpredictability

The Trump administration's alliance policy is redefined not as a reciprocal relationship but as a bilateral transaction[3]. This transaction is based on the premise that U.S. interests come first[3]. In South Korea, this unpredictability is already being felt. The significant scaling back of U.S.-South Korea joint military exercises at President Trump's direction is a prime example[13][17]. The Ulchi Freedom Shield exercise proceeded as scheduled but was shortened by President Trump's order[13].

Interestingly, it has been observed that this unpredictability is paradoxically becoming an incentive for cooperation among Asian allies[13]. This means that the motivation to reduce dependence on the single variable of the United States is at work simultaneously in countries like South Korea and Japan.

Economic Structure: The Tariff-Security Linkage Package

This pressure regarding the Cheongung-II is not limited to a security issue. Targeted semiconductor tariffs, designation as a transshipment risk country, and defense cost-sharing demands are being pursued as an interconnected negotiating package[5]. If the responses of the Ministry of Trade, Industry and Energy, the Ministry of Foreign Affairs, and the Ministry of National Defense are fragmented, there is a risk that the U.S. side will exploit differences in their positions to maximize concessions[5]. The possibility that the Cheongung-II issue will also be treated as part of this package cannot be ruled out.

3. Comparison with Historical Precedents and Similar Cases

The Case of Taiwan: The Politics of Delay

In the process of acquiring $14.5 billion worth of Patriot PAC-3 and NASAMS systems, Taiwan received at least four different explanations for the delays[9]. The acting Under Secretary of the Navy explicitly cited the need to secure ammunition for operations in Iran as the reason[9]. This sets a precedent for the United States arbitrarily adjusting its arms supply priorities for allies based on its own needs on other fronts. The pressure on South Korea to sell the Cheongung-II rests on the same logical structure. However, the direction is opposite. In Taiwan's case, the U.S. is delaying sales to an ally; in South Korea's case, it is pressuring an ally to sell its own weapon system to a third country. The common thread is that the shortfall in U.S. production capacity is transferred in a way that constrains the autonomy of its allies.

The Case of Europe: Demands for Repayment and Confusion over Sales Suspensions and Resumptions

The pressure on Europe preceded that on South Korea and was more overt. President Trump announced he would demand repayment for the tens of billions of dollars in aid provided free of charge to Ukraine and NATO during the Biden administration[10][14]. Simultaneously, he suggested a halt to arms sales to allies[6][12], only to reverse himself on the same day by saying they would resume soon[11]. This inconsistency in messaging reveals a decision-making structure where policy is expressed impulsively through the president's personal social media, without systematic review. Given that the Cheongung-II demand on South Korea was made through the same channel and in the same manner, it should be seen more as a pressure signal than a fully formed policy.

There is also the case of Ukraine requesting to purchase Patriot PAC-3 systems using a €90 billion loan from the EU to fill the gap left by the United States[19]. EU Commission President von der Leyen confirmed this[19]. For Ukraine, this is an attempt to reduce its dependence on the United States as a single supplier, and the Cheongung-II should also be seen as being discussed in the context of this demand for diversification.

The Falklands Case: The Levering of Security Assets

With respect to the United Kingdom, President Trump, while pressing for increased defense spending, mentioned that the U.S. position on the Falkland Islands was "one of several things under review"[15]. This is a signal that even sovereignty issues can be put on the table to induce NATO members to fulfill their defense spending commitments[15]. This demonstrates a pattern of the Trump administration selectively using issues sensitive to an allied country as leverage when applying pressure. In South Korea's case, that leverage was the U.S.-South Korea joint military exercises, a core component of deterrence against North Korea[13][17]. This time, a domestically developed defense asset, the Cheongung-II, is being used as leverage.

4. Key Variables Shaping Future Developments

First, the actual state of U.S. ammunition stockpiles is a key factor. As long as reports of stockpile depletion continue despite President Trump's denials[6][10], demands for alternative supplies from allies are likely to be repeated. How the U.S. Department of Defense officially handles this issue will determine the intensity of the next round of pressure.

Second is whether Ukraine's independent procurement channel with the EU materializes. If the EU approves the request to purchase Patriot systems using the €90 billion loan[19], Ukraine's dependence on the United States and South Korea will be relatively reduced. Conversely, if this channel is delayed, the demand for the Cheongung-II could become more specific.

Third is the direction taken on the Hormuz deployment issue. As the demands for the deployment and the Cheongung-II sale were made simultaneously on the same day[4], the choice the South Korean government makes on the deployment issue could affect the intensity of the pressure for the arms sale. This means the two tracks are not entirely separate issues.

Fourth is the progress of U.S.-South Korea negotiations on tariffs and semiconductors. Considering the observation that security and economic demands are linked in a single package[5], whether there is progress on issues like targeted semiconductor tariffs or designation as a transshipment risk country could act as a variable influencing the pace and intensity of the pressure regarding Cheongung-II.

Fifth are the positions of South Korean public opinion and the defense industry. Regarding troop deployment, a cautious view clearly prevails, framing it as an issue concerning the lives of South Korean citizens.[1][17] While the export of the Cheongung-II is a different matter, as a direct arms export to a belligerent in the Ukraine war, it could conflict with South Korea's relations with Russia and its existing policy toward Moscow. How this issue is handled in the domestic public discourse will be a variable constraining the government's options.